Conventionally, several vibration damping systems are presented. The vibration damping system is mounted on a device inside of which a vibration source is provided and damps the vibration produced by the vibration source.
For example, the patent document 1 discloses a vibration damping system wherein an actuator as being a vibration applying device is mounted on a frame of a vehicle, vibration transmitted from an engine as being a vibration source is detected, an offset vibration that offsets the vibration is generated by the above-mentioned actuator so that the vibration by the engine is damped.
This kind of the vibration damping system is generally constructed by mounting a vibration detecting device at a desired position of the frame and by reducing vibration at a position where the vibration detecting device is mounted. With this arrangement, the vibration by the vibration applying device that is arranged at a position different from a position where the vibration detecting device is mounted is transmitted to the position where the vibration detecting device is mounted through the frame so that the vibration generated by a vibration source is reduced by producing an offset vibration at this position. More specifically, a single vibration damping system as a whole is composed of the frame on which the vibration applying device is mounted.
In addition, in case that element components such as the vibration detecting device or the vibration applying device are once mounted on the frame so as to constitute the integrally formed vibration damping system, it becomes difficult to dismount these element components from the frame. As a result of this, in case of verifying the function after constituting the vibration damping system, it is required to conduct diagnosis without dismounting the element components.
Then, it can be conceived that the control device to control the vibration applying device comprises a failure diagnosis mode to diagnose whether there is failure or not by driving the vibration applying device in a previously determined condition wherein each element component is remained to be mounted on the frame and verifying whether the vibration damping system runs properly or not, in addition to a normal mode to damp vibration.